Apparently this is a rare word whose birthdate we know, at least sometime before 1884. Below is from the American Heritage Dictionary also cited in Webster's Collegiate.

We are indebted to a British comedian for the word spoof. Sometime in the 19th century Arthur Roberts (1852-1933) invented a game called Spoof, which involved trickery and nonsense. The first recorded reference to the game in 1884 refers to its revival. It was not long before the word spoof took on the general sense "nonsense, trickery," first recorded in 1889. The verb spoof is first recorded in 1889 as well, in the sense "to deceive." These senses are now less widely used than the noun sense "a light parody or satirical imitation," first recorded in 1958, and the verb sense "to satirize gently," first recorded in 1927.

I have always placed spoofs in the lighthearted genre. I just discovered that all the e-mails I have gotten purporting to be from someone I know are e-mail spoofs. Someone always has to try to spoil a good word.